A liquid crystal display device (LCD), having various advantages such as being easy to make thin and light, able to reduce the consumption power and difficult to cause flickers, is used in various fields such as televisions and medical equipment. On the other hand, in addition to a problem in that, depending on an angle by which a viewer sees a liquid crystal display screen, light leakage and gradation reversal phenomena are caused to result in a narrow viewing angle, there is a problem in that the irregular color is caused on a liquid crystal display screen or the contrast is deteriorated.
In order to overcome the problems, there has been proposed a liquid crystal display device provided with an optical element that controls a state of light exiting from a liquid crystal cell or light incident on a liquid crystal cell.
In that case, as an optical element, proposed is an optical element that uses, other than a film material obtained by uniaxially or biaxially stretching a triacetyl cellulose film, a layer in which liquid crystal molecules are aligned in a specified direction and fixed.
Patent document 1 proposes a viewing angle compensation film made of a nematic liquid crystal polymer of which an intrinsic refractive index value is positive when molecular chains are aligned in a normal line direction of a film surface. Patent document 1 discloses that the viewing angle compensation film is obtained in such a manner that a vertical alignment film is formed on a surface of a glass substrate or the like with an alkyl silicone-based or fluoroalkyl silicone-based surface treatment agent, a cell is prepared therefrom, and liquid crystal molecules are encapsulated in the cell to photo-polymerize the liquid crystal molecules.
Patent document 2 proposes a method of producing a liquid crystal layer where a polymerizable liquid crystal compound is coated on a vertical alignment film formed on a substrate to thereby homeotropically align the liquid crystal compound. In the method, a long-chain alkyl dendrimer derivative is used as a forming agent of the vertical alignment film. Furthermore, Patent document 2 discloses that, according to the method, a film material provided with a homeotropically aligned liquid crystal layer is obtained and the film material may be used as an optical film such as a retardation film.
Patent document 3 proposes a method of producing a homeotropically aligned liquid crystal film, the method including coating on a substrate on which no vertical alignment film is disposed a side-chain type liquid crystal polymer that contains a monomer unit containing a liquid crystalline fragment side-chain and a monomer unit containing a non-liquid crystalline fragment side-chain, homeotropically aligning the liquid crystal polymer in a liquid crystal state, and then fixing the liquid crystal polymer with the aligned state maintained.
Patent document 4 proposes a method of producing a homeotropically aligned liquid crystal layer, the method including forming on a substrate on which no vertical alignment film is disposed a binder layer and an anchor coat layer from the substrate side, coating a side-chain type liquid crystal polymer on the anchor coat layer to homeotropically align the side-chain type liquid crystal polymer, and then fixing the side-chain type liquid crystal polymer with the homeotropically aligned state maintained. In the method, as the side-chain type liquid crystal polymer, one that may form a homeotropically aligned liquid crystal layer on a substrate on which no vertical alignment film is disposed is used.
Patent document 1: Japanese Patent Application Laid-Open No. 05-142531
Patent document 2: Japanese Patent Application Laid-Open No. 2002-174724
Patent document 3: Japanese Patent Application Laid-Open No. 2002-174725
Patent document 4: Japanese Patent Application Laid-Open No. 2003-121852